The present disclosure relates generally to a power transmission device operable to selectively transfer torque between first and second sets of drivable wheels of a vehicle. More particularly, the present disclosure describes a torque transfer device including a clutch integrally associated with driving axle components.
Due to increased demand for four-wheel drive vehicles, many power transmission systems are typically being incorporated into vehicle driveline applications for transferring drive torque to the wheels. Many vehicles include a power transmission device operably installed between the primary and secondary drivelines. Such power transmission devices are typically equipped with a torque transfer mechanism for selectively transferring drive torque from the primary driveline to the secondary driveline to establish a four-wheel drive mode of operation. At least one known torque transfer mechanism includes a dog-type lock-up clutch that may be selectively engaged for rigidly coupling the secondary driveline to the primary driveline when the vehicle is operated in four-wheel drive mode. Drive torque is delivered only to the primary driveline when the lock-up clutch is released and the vehicle operates in a two-wheel drive mode.
Another type of power transmission device is operable for automatically directing drive torque to the secondary wheels without any input or action on the part of a vehicle operator. When traction is lost at the primary wheels, the four-wheel drive mode is entered. Some transfer cases are equipped with an electrically-controlled clutch actuator operable to regulate the amount of drive torque transferred to a secondary output shaft as a function of changes in vehicle operating characteristics such as vehicle speed, throttle position and steering angle. Typically, the power transfer device includes a clutch positioned within the transfer case housing.
While many power transfer devices are currently used in four-wheel drive vehicles, a need exists to advance the technology and recognize the system limitations. For example, the size, weight and packaging requirements of the power transmission device may make such system costs prohibitive in some four-wheel drive applications.